Explicitly make ScriptInterface a Compartment wrapper.
ScriptInterface is now a wrapper around a JSCompartment, and thus always has a well-defined global.
The error reporter is moved to ScriptRuntime in anticipation of that handling JSContext in a later diff.
Part of the SM52 migration, stage: SM45 compatible.
Patch by: Itms
Tested By: Freagarach
Differential Revision: https://code.wildfiregames.com/D3090